Part 2 of 2

Chart C-10 Part 2 Of 2:

A/C Circuit:

Circuit Description:
The A/C clutch control relay is PCM controlled to delay A/C clutch engagement after the A/C is turned "ON." This allows the PCM to adjust engine RPM before the A/C clutch engages.

The PCM will engage the A/C clutch anytime A/C has been requested unless any of the following conditions exist:

^ High coolant temperature.
^ Wide open throttle.
^ High engine RPM.
^ High A/C system pressure.
^ Low system pressure.
^ Any A/C DTC set

The PCM can determine A/C has been requested by a voltage signal received from the A/C control head. When the A/C select switch closes, the A/C request voltage signal is applied to the PCM A/C request input. This is shown on the Tech 1 as A/C request "ON." A 3-wire A/C refrigerant pressure sensor is used to monitor A/C system pressure. If the A/C refrigerant pressure is greater than 430 psi or lower than 0 psi, the A/C clutch will not engage.

The A/C refrigerant pressure sensor uses DTCs 66, 67 and 70 to indicate sensor or sensor circuit malfunctions. If the A/C refrigerant pressure sensor signal wire becomes open or shorted to ground, DTC 66 will set. If the signal line is shorted to voltage a DTC 70 is set. If the A/C clutch engages and no pressure change is detected, a DTC 67 will set.

When a request for A/C has been detected by the PCM, the PCM will ground the A/C clutch control relay drive circuit, the relay contacts will close, and current will flow through the relay to the A/C compressor clutch via the A/C compressor low pressure cutoff switch.